Hi anyone would help mewith this error 'R_tilde = builtin('subsref',L_tilde,Idx)'
3 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
syms f(t) cos sin M m1 m2 xddot xddotsq l1 l2 L1 l2 alpha alphadot alphaddot alphadot beta betaddot betadot g gamma sq theta xddot
eqn1=-f(t)*(M+m1+m2)*xddot + (m1*l1+m2*L1)*alphaddot*cos*alpha + m2*l2*betaddot*cos*beta - (m1*l1+m2*L1)*alpha*sq*sin*alpha - m2*l2*betadot*sq*sin*beta;
eqn2=(m1*l1*sq+m2*L1*sq+l1)*alphaddot + (m1*l1*m2*L1)*xddot*cos*alpha + (m2*l2*L1*betaddot*cos*gamma) + (m2*l2*L1*beta*sq*sin*gamma) - g(m1*l1+m2*L1)*(sin*alpha);
eqn3=(m2*L1*sq+l2)*betaddot + (m2*l2)*xddot*(cos*beta) + (m2*l2*L1)*alphaddot*(cos*gamma) - (m2*l2*L1)*alphadot*sq*(sin*gamma) - (m2*g*l2*sin*beta);
sol = solve([eqn1, eqn2, eqn3], [f(t),cos,sin,M,m1,m2,xddot,xddotsq,l1,l2,L1,l2,alpha,alphadot,alphaddot,alphadot,beta,betaddot,betadot,g,gamma,sq,theta,xddot]);
xSol = sol.x;
alphaSol = sol.alpha;
gammaSol = sol.gamma;
2 commentaires
Steven Lord
le 20 Juil 2021
Please show us the full and exact text of the error message (everything displayed in red and/or orange in the Command Window when you run the code, exactly as it is displayed in the Command Window.)
Réponses (1)
Steven Lord
le 20 Juil 2021
A couple comments / suggestions:
syms f(t) cos sin M m1 m2 xddot xddotsq l1 l2 L1 l2 alpha alphadot alphaddot alphadot beta betaddot betadot g gamma sq theta xddot
The identifiers cos, sin, alpha, beta, and gamma each already have meanings in MATLAB. By defining them as symbolic variables you will not be able to call the cosine, sine, alpha (graphics transparency), beta (special function), or gamma (special function) functions while those symbolic variables exist.
eqn1=-f(t)*(M+m1+m2)*xddot + (m1*l1+m2*L1)*alphaddot*cos*alpha + m2*l2*betaddot*cos*beta - (m1*l1+m2*L1)*alpha*sq*sin*alpha - m2*l2*betadot*sq*sin*beta;
eqn2=(m1*l1*sq+m2*L1*sq+l1)*alphaddot + (m1*l1*m2*L1)*xddot*cos*alpha + (m2*l2*L1*betaddot*cos*gamma) + (m2*l2*L1*beta*sq*sin*gamma) - g(m1*l1+m2*L1)*(sin*alpha);
You can't ask for element m1*l1+m2*L1 of g like you did in the last term on the line above. If I'd written:
myX = 1:10;
result = myX(g)
what would you expect result to be? I'm guessing you meant to multiply g by that expression but forgot the *.
eqn3=(m2*L1*sq+l2)*betaddot + (m2*l2)*xddot*(cos*beta) + (m2*l2*L1)*alphaddot*(cos*gamma) - (m2*l2*L1)*alphadot*sq*(sin*gamma) - (m2*g*l2*sin*beta);
sol = solve([eqn1, eqn2, eqn3], [f(t),cos,sin,M,m1,m2,xddot,xddotsq,l1,l2,L1,l2,alpha,alphadot,alphaddot,alphadot,beta,betaddot,betadot,g,gamma,sq,theta,xddot]);
You've got three equations in many more than 3 unknowns. That could be a problem.
Based on your naming scheme, I'm guessing you're trying to solve a system of differential equations. If I'm correct you might want to try the approach described on this documentation page instead.
0 commentaires
Voir également
Catégories
En savoir plus sur Calculus dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!